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21.06.10 E. Coli survives at temperatures greater than 42 ° C thanks to GroE

Scientists from TUM have on E. coli Bacteria is studying how organisms evolve to adapt to higher temperatures

Because it is small, robust and reproduces quickly, the intestinal bacterium Escherichia coli is one of the most important “workhorses” in biotechnology. It produces insulin and many other pharmaceutically important substances for us. Usually the bacterium feels most comfortable at 37 ° Celsius. Higher temperatures cause stress in the small organism, temperatures above 46 ° Celsius are already fatal. Scientists from the Technical University of Munich (TUM) now have E. coli Bacteria is studying how organisms evolve to adapt to higher temperatures.

Fig. 1: Electron microscope image of thin sections more heat-resistant Escherichia coli-Bacteria
Source: Jeannette Winter, TUM

The bacterium Escherichia coli is not only at home in the human intestine, it is also one of the most important “workhorses” in the laboratory. A large number of pharmaceutically important substances are now biotechnologically modified by genetically engineered ones E. coli-Bacteria produced, for example insulin. While the rule of thumb in chemical production is that a temperature that is ten degrees higher results in a doubling of the reaction speed, the situation in biotechnology is much more complicated. Although productivity increases from E. coli At higher temperatures initially, above 42 ° Celsius, the organism comes under increasing stress and produces less useful proteins. Temperatures above 46 ° Celsius are for wild-typeE. coli already fatal.

The team around Jeannette Winter, biochemist and head of the Emmy Noether group “Oxidative Stress” in the Chemistry Department of the Technical University of Munich, has now succeeded in E. coli-Bacteria by evolution over several years gradually to grow a much higher heat resistance. Your bacteria now grow at temperatures of 48.5 ° Celsius. But here it seems for the organism E. coli a natural limit to exist. The researchers did not reach higher growth temperatures.

Fig. 2: Crystal structure of GroE
Source: Z. Xu, et al., PDB, DOI: 10.2210 / pdb1aon / pdb

Compared to a control population bred at 37 ° Celsius from the same ancestors, the heat-resistant bacteria contained the GroE, known as a heat protection protein, in a 16-fold higher concentration even under normal conditions. However, heat resistance has its price: Since the organism carries changes in the genetic material due to the constant stress and puts a lot of energy into the production of heat protection proteins, it grows more slowly than its ancestors.

There is a complex process behind this: Every protein consists of a long chain of amino acids. It is only through artful folding into a three-dimensional structure that it becomes a functioning protein. Proteins called chaperones, like GroE, help here. It stabilizes proteins that become unstable at higher temperatures and helps to bring proteins that have become more unstable due to mutations into their functional form. "The ability of the heat-resistant bacteria to be able to produce much higher concentrations of GroE is a decisive factor for survival under these conditions," says Jeannette Winter.

In addition to the evolutionary biological aspects, the study by the working group provides valuable information on how organisms adapt to changing environmental conditions. "A better understanding of the work of the chaperones could also open new ways for the targeted breeding of organisms for special tasks," says Jeannette Winter. "These are not only bacteria for the production of pharmaceutically interesting proteins, but also, for example, bacteria that can break down environmental toxins under harsh environmental conditions."


Evolution of Escherichia coli for Growth at High Temperatures
B. Rudolph, et. al., J. Biol. Chem.2010. DOI: 10.1074 / jbc.M110.103374

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E. Coli survives at temperatures greater than 42 ° C thanks to GroE

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